Jawabanmu

2014-06-10T20:26:13+07:00
K = π × 2r
12,56 = 3,14 × 2r
12,56 : 3,14 = 2r
       4          = 2r
       r           = 2 cm

L = π × r²
L = 3,14 × 2²
L = 3,14 × 4
L = 12,56 cm²